Apparatus and method for tripping a safety system for the protection of an occupant of a vehicle

Abstract

An apparatus and method for actuating a safety system for protecting an occupant of a motor vehicle measures the acceleration of the vehicle with a first sensor along a first axis oriented substantially parallel to the forward direction of motion of the vehicle. The acceleration of the vehicle is also measured with a second sensor along a second axis oriented at an angle relative to the first axis. The acceleration signal generated by the first sensor is evaluated by an analog processor and the acceleration signal generated by the second sensor is evaluated by a digital processor. The safety system is then actuated based upon both the analog and digital evaluations.

We claim: 
     
       1. A system for actuating at least one safety device for the protection of an occupant of a vehicle, comprising: a first acceleration sensor for sensing a first acceleration of the vehicle and for providing a first acceleration signal based thereon;   a second acceleration sensor for sensing a second acceleration of the vehicle and for providing a second acceleration signal based thereon;   a digital controller coupled to the first and second acceleration sensors for providing a first trigger signal as a function of the first and second acceleration signals, the first trigger signal being indicative of whether the safety device should be actuated;   an analog evaluation circuit for receiving the first acceleration signal and the first trigger signal and for providing a second trigger signal as a function of the first acceleration signal and the first trigger signal at an analog circuit output of the analog evaluation circuit, the second trigger signal indicating whether the safety device should be actuated; and   an output stage having an input connected to the analog circuit output for receiving the second trigger signal from the analog evaluation circuit and for actuating the safety device as a function of the second trigger signal.   
     
     
       2. The system according to claim 1, wherein the first acceleration is along an axis oriented in a direction of forward motion of the vehicle. 
     
     
       3. The system according to claim 1, wherein the second acceleration is along an axis oriented at a right angle relative to a direction of forward motion of the vehicle. 
     
     
       4. The system according to claim 1, wherein the first acceleration is along a first axis and the second acceleration is along a second axis oriented at an angle relative to the first axis. 
     
     
       5. The system according to claim 4, wherein the first axis is oriented in a direction of forward motion of the vehicle. 
     
     
       6. The system according to claim 5, wherein the second axis is oriented at a right angle relative to the direction of forward motion of the vehicle. 
     
     
       7. The system according to claim 4, wherein the second axis is oriented at a right angle relative to the first axis. 
     
     
       8. The system according to claim 1, wherein the digital controller determines, in a digital manner, an occurrence of a collision of the vehicle. 
     
     
       9. The system according to claim 1, wherein the analog evaluation circuit determines, in an analog manner, an occurrence of a collision of the vehicle. 
     
     
       10. The system according to claim 9, wherein the digital controller determines, in a digital manner, an occurrence of a collision of the vehicle. 
     
     
       11. The system according to claim 1, further comprising: a first low-pass filter coupled between the first acceleration sensor and the digital controller; and   a second low-pass filter coupled between the second acceleration sensor and the digital controller.   
     
     
       12. The system according to claim 1, further comprising an analog-to-digital converter having a first input coupled to the first acceleration sensor, a second input coupled to the second acceleration sensor, and an output coupled to the digital controller. 
     
     
       13. A system for actuating at least one safety device for the protection of an occupant of a vehicle, comprising: a first acceleration sensor for sensing a first acceleration of the vehicle and for providing a first acceleration signal based thereon;   a second acceleration sensor for sensing a second acceleration of the vehicle and for providing a second acceleration signal based thereon;   a first analog-to-digital converter coupled to an output of the first acceleration sensor;   a second analog-to-digital converter coupled to the output of the first acceleration sensor and to an output of the second acceleration sensor;   a first digital controller coupled to an output of the first analog-to-digital converter for providing a first trigger signal indicative of whether the safety device should be actuated;   a second digital controller coupled to the first digital controller and to an output of the second analog-to-digital converter for providing a second trigger signal indicative of whether the safety device should be actuated;   an analog evaluation circuit for receiving the first acceleration signal and the first trigger signal and for providing a third trigger signal as a function of the first acceleration signal and the first trigger signal at an analog circuit output of the analog evaluation circuit, the third trigger signal being indicative of whether the safety device should be actuated; and   an output stage having an input connected to the analog circuit output for actuating the safety device as a function of the third trigger signal.   
     
     
       14. The system according to claim 13, wherein the output stage is further connected to an output of the first digital controller for actuating the safety device as a function of the first and third trigger signals. 
     
     
       15. The system according to claim 13, wherein the first digital controller receives the second trigger signal from the second digital controller for providing the first trigger signal as a function of the second trigger signal. 
     
     
       16. The system according to claim 13, wherein the first acceleration is along an axis oriented in a direction of forward motion of the vehicle. 
     
     
       17. The system according to claim 13, wherein the second acceleration is along an axis oriented at a right angle relative to a direction of forward motion of the vehicle. 
     
     
       18. The system according to claim 13, wherein the first acceleration is along a first axis and the second acceleration is along a second axis oriented at an angle relative to the first axis. 
     
     
       19. The system according to claim 18, wherein the first axis is oriented in a direction of forward motion of the vehicle. 
     
     
       20. The system according to claim 19, wherein the second axis is oriented at a right angle relative to the direction of forward motion of the vehicle. 
     
     
       21. The system according to claim 18, wherein the second axis is oriented at a right angle relative to the first axis. 
     
     
       22. The system according to claim 13, wherein at least one of the first and second digital controllers determines, in a digital manner, an occurrence of a collision of the vehicle. 
     
     
       23. The system according to claim 13, wherein the analog evaluation circuit determines, in an analog manner, an occurrence of a collision of the vehicle. 
     
     
       24. The system according to claim 23, wherein at least one of the first and second digital controllers determines, in a digital manner, an occurrence of a collision of the vehicle.